Engine

ABSTRACT

An engine is disclosed that incorporates components purely or predominantly rotational components. An engine including a rotor and a stator, in which a combustion chamber is defined in the stator and a fluid receiving chamber is defined in the rotor, in which combustion gas can expand from the combustion chamber into the receiving chamber, whereby momentum is transferred from the combustion gas to the rotor.

The present invention relates to an engine.

In particular, the invention relates to an internal or externalcombustion engine that employs purely or predominantly rotationalmembers.

The majority of internal combustion engines in use today employreciprocating pistons. However, it is recognised that the presence ofreciprocating components imposes a limit upon the maximum speed ofoperation of an engine. Moreover, the need to contain the forcesassociated with reciprocating components mandates the use of componentsof substantial weight. For this reason, attempts have been made todevise engines that employ components having purely or predominantlyrotary components. To date, the most successful rotary piston engine isthe “Wankel” engine, named after its German inventor. However, this unitalthough simple, has had limited commercial success due to severalreasons. The foremost of these is its reputation for suffering fromsealing problems, followed by low torque at low engine speed, fuelinefficiency and relatively high pollution levels. The unit also suffersfrom the need for careful maintenance and its speed of operation must belimited, if seal failure is to be avoided. Moreover, the piston of aWankel engine (at least, of the type most commonly used in practice)undergoes motion that is not purely rotary; it also has an oscillatorycomponent, and this leads to residual vibration.

Gas turbine engines are also known. In such engines, expandingcombustion gas is caused to impinge upon blades of a rotor, and therebyimpart a torque to the rotor. A gas turbine has the advantage that itsrotor undergoes purely rotational motion, and it can therefore operateat high speed with a minimum of vibration. However, such enginestypically operate efficiently only within a relatively narrow band ofengine speeds which renders them unsuited to operation in manycircumstances, a most important example of which is as an engine for amotor road vehicle.

An aim of the invention is to provide an engine that has predominantlyrotary components, and which overcomes or at least ameliorates somedisadvantages of known engines.

From a first aspect, the invention provides an engine including acombustion assembly comprising a rotor and a stator, in which acombustion chamber is defined in the stator and a fluid receivingchamber is defined in the rotor, in which combustion gas can expand fromthe combustion chamber into the receiving chamber, whereby momentum istransferred from the combustion gas to the rotor.

Such an engine may be embodied with a minimum of components, none ofwhich undergo oscillatory movement.

Such an engine may typically have a plurality of rotor expansionchambers into which combustion gas can expand in turn. Most commonly,the rotor expansion chambers are of different volumes. In particular,the rotor expansion chambers are typically of successively increasingvolumes. The combustion chamber is advantageously of volume larger thanseveral of the rotor expansion chambers.

In preferred embodiments, the stator has a plurality of stator expansionchambers into which gas can expand from the chambers of the rotor.Typically, the rotor expansion chambers are of different volumes. Inparticular, the rotor expansion chambers may be of successivelyincreasing volumes.

In preferred embodiments the rotor has a transfer chamber through whichcombustion gas can pass into the combustion chamber during a portion ofthe rotation of the rotor.

An engine embodying the invention may be provided with spark ignitionapparatus in association with the combustion chamber for igniting acharge of combustible fluid received therein. Typically, the ignitionapparatus includes a spark plug.

In an engine embodying the invention, either one or both of the rotorand stator may be formed from a material that has self-lubricatingproperties. For example, either the rotor or the stator may be formedfrom spheroidal graphite iron.

Alternatively or additionally, an engine embodying the invention mayhave an oil mist injector operative to inject an oil mist into a spacebetween the rotor and the stator. Typically, such an oil mist isinjected at a position in advance of the combustion chamber.

An engine embodying the invention may, moreover, have a lubricatingbrush to add lubricating material such as graphite between the statorand the rotor.

In one class of embodiments of an engine, the rotor is shaped as a dischaving chambers opening to the periphery of the disc. In suchembodiments, the engine preferably has a gap control system forcontrolling a separation between the rotor and the stator duringoperation of the engine. Such a gap control system may operate to movethe stator radially with respect to the rotor.

In such embodiments, the rotor may comprise a rotor assembly thatincludes a rotor casting. The rotor casting may be shaped as a disc,having peripheral openings into voids formed therein. The rotor assemblymay further comprise end plates secured to the rotor casting to closethese voids axially. Several such rotor castings may be assembledtogether between endplates to provide a combustion assembly of greatercombustion capacity, giving rise to a convenient modular form ofconstruction.

In embodiments according to the last-preceding sentence, a spacer may bedisposed between adjacent rotor castings to aid in removal of heat fromthe combustion assembly, and from the rotor castings in particular. Thespacer may typically include a through passage in alignment with coolingfluid ducts of the rotor castings.

The stator assemblies may likewise comprise a stator assembly thatincludes a stator casting. The stator casting may be shaped as a topartially surround the rotor assembly, having openings into voids formedtherein. The stator assembly may further comprise end plates secured tothe stator casting to close these voids axially. Several such statorcastings may be assembled together between endplates to provide acombustion assembly of greater combustion capacity.

In embodiments according to the last-preceding sentence, a spacer may bedisposed between adjacent stator castings to aid in removal of heat fromthe combustion assembly, and from the stator castings in particular.Such a spacer may be formed with holes to link the combustion chambersof the various stator castings in an axial direction. Alternatively, oradditionally, combustion mixture may be introduced into each of thecombustion chambers.

The optional rotor and/or stator spacer may be provided with fins toremove heat therefrom.

In another class of embodiments, of an engine, the rotor is shaped as afrustum, having chambers opening to its periphery. In such embodiments,the stator typically partially surrounds the rotor. Such embodiments mayhave a gap control system for controlling a separation between the rotorand the stator during operation of the engine. The gap control systemmay operate to move the stator axially with respect to the rotor.

In embodiments including a gap control system, the gap control systemmay include a non-contact sensor. Such a sensor may operate bycapacitive sensing, inductive sensing or a combination of capacitive andinductive sensing.

In yet another class of embodiments, the stator are both disc shaped,the combustion chamber being defined between flat faces of the rotor andthe stator. In such embodiments, a gap control typically operates tomove the stator axially with respect to the rotor.

In embodiments according to either of the last two preceding paragraphs,the rotor and/or the stator may comprise a casting and one or moreendplates, as described above.

An engine embodying the invention may further include a compressor forsupplying combustion air to the combustion assembly. The compressor maybe driven by the rotor. In a convenient construction, the compressor andthe rotor may be carried on a common shaft or upon interconnectedcoaxial shafts. Preferably, an intercooler is disposed between thecompressor and the combustion assembly operative to remove heat from thecombustion air, and thereby improve volumetric efficiency of the engine.

For spark ignition embodiments, the compressor may deliver combustionair at a pressure in the range of 4 to 7 Bar. Where combustion aircharge cooling is provided (for example, in the form of an intercooler)this pressure may be increased to a range of 6 to 12 Bar. Incompression-ignition embodiments, the pressure may typically be in therange of 9 to 15 Bar. Where combustion air charge cooling is provided(for example, in the form of an intercooler) this pressure may beincreased to a range of 20 to 30 Bar.

In some embodiments, fuel is injected into a stream of combustion airexternally of the combustion assembly. Alternatively or additionally,fuel may be injected into a chamber within the combustion assembly.

In addition to fuel and air, water may be introduced into the combustionchamber together with air and fuel. In some of such embodiments, thewater may expand as vapour, during combustion, the water vaporises andexpands into the receiving chamber and transfers at least some of itsmomentum to the rotor.

From another aspect, the invention provides a combustion engineincluding a rotor and a stator, said stator carrying a first set ofcombustion chambers and said rotor carrying a second set of combustionchambers, the arrangement being such that during operation said rotorrotates relative to said stator and a working fluid is transferred insuccession between the combustion chambers of said first and secondsets, thereby driving the rotation of the rotor.

By means of this arrangement, the engine can be provided with combustionchambers of a shape and size optimised for a particular intendedapplication. Moreover, the rotor is typically arranged such that itsmotion is purely rotational, with no oscillatory component.

Important to this engine's success is a novel thermodynamic cycle thatis employed in the ‘hot’ portion of the unit. The engine may have eithera single or multistage separate compressor section to achievecompression of the working fluid, which is normally air.

According to a further aspect of the present invention there is provideda combustion engine including a rotor and a stator, said stator carryinga first set of combustion chambers and said rotor carrying a second setof combustion chambers, the arrangement being such that during operationsaid rotor rotates relative to said stator and a working fluid istransferred in succession between the combustion chambers of said firstand second sets, thereby driving the rotation of the rotor.

Advantageously, one or more types of combustion chamber are provided,including one or more of the types referred to hereinafter as ‘mother’,‘maid’ and ‘daughter’ chambers.

Advantageously, the rotor and/or the stator include a set of daughterchambers that increase progressively in volume.

At least some of the chambers are preferably retort-shaped.

The working fluid is preferably transferred between the chambers by aprocess referred to hereinafter by the term “Harmonic Gas Fluctuations”.

Advantageously, the engine includes a compressor for supplying acombustible mixture of fuel and air to the combustion chambers.

According to a further aspect of the invention there is provided acombustion engine including a rotor and a stator, said engine employinga cadence-recursive expansion process for driving the rotation of therotor. The cadence-recursive expansion process is described in moredetail below.

An engine embodying this invention may be designed to be reliable andmay avoid sealing problems by virtue of its high speed of operation andspecific design features. It may not suffer from pollution effects orlow torque levels. It may also be extremely simple, having (at leasttheoretically) just one rotating part in its simplest embodiment.Moreover, an engine embodying the invention may have an extremely highspecific power output level with low weight, thus providing a power toweight ratio of the same order as the most efficient gas turbinescurrently available. The output of an engine embodying the invention istypically principally shaft power, not thrust as in a gas turbine unit.Hence it may be suitable to be used for prime moving applications,ranging from all types of road transport to all types of aeronauticalapplications, including helicopters and VTOL aircraft. It may also besuitable for static power generation, co-generation and marineapplications. Due to the combination of rotary action and the uniquethermodynamic cycle employed it may be fuel-efficient and because of itsextreme simplicity in principle, it may be inexpensive to manufacture.

Throughout this application, comparisons are drawn with comparablereciprocating designs to illustrate points being discussed.

An embodiment of the invention will now be described in detail, and withreference to the accompanying drawings, in which:

FIG. 1 is a sectional general arrangement drawing of a spark-ignitionengine embodying the invention;

FIG. 1a is a diarammatic axial sectional view of a compressor of theengine of FIG. 1;

FIGS. 2a and 2 b are, respectively, elevational and transversecross-sectional views of a compressor rotor of the embodiment of FIG. 1;

FIGS. 3a and 3 b are, respectively, front and a part-sectional side viewof a modified compressor rotor casing assembly;

FIG. 4 is a perspective view of a component of the rotor casing assemblyof FIGS. 3a and 3 b;

FIGS. 5, 6 are axial and transverse sectional views of an intercoolerbeing part of the engine of FIG. 1;

FIG. 7 is a part sectional view of a rotor and a stator of a combustionassembly of the engine of FIG. 1 showing their relationship with oneanother;

FIGS. 8 and 8a are a perspective and axial views of a rotor casting of arotor assembly of the engine of FIG. 1;

FIG. 9 shows an end plate for the rotor casting of FIG. 8;

FIGS. 10 and 10a are perspective and axial views of a stator casting ofthe engine of FIG. 1;

FIG. 11 is an end plate for the stator casting of FIG. 10;

FIGS. 12a to 12 e are schematic cross-sectional views of part of therotor and the stator of FIG. 2 during a combustion cycle, with FIG. 12abeing a section along the line A-A′ of FIG. 7;

FIG. 13 is a section along line A—A in FIG. 12a;

FIG. 14a is a first exhaust configuration suitable for use with theengine of FIG. 1;

FIG. 14b is an alternative exhaust configuration suitable for use withthe engine of FIG. 1;

FIG. 15 is a circuit diagram for an engine misfiring detection systemsuitable for use with the engine of FIG. 1;

FIG. 16 shows a lubricant brush suitable for use with the engine of FIG.1;

FIGS. 17 and 18 show, diagrammatically, relative movement of the statorand the rotor of the engine of FIG. 1.

FIGS. 19 and 20 are cross-sectional views of an alternative embodimentof the invention;

FIG. 21 is a cross-sectional view of another alternative embodiment ofthe invention;

FIG. 22 to 24 show alternative arrangements for maintaining a controlledrotor/stator gap;

FIG. 25 show an arrangements for maintaining a controlled rotor/statorgap and monitoring bearing status;

FIG. 26 shows a non-contact gap control system incorporating a capacitorplate as a sensor;

FIG. 27 is a diagram of additional circuitry for use in a combined gapcontrol, bearing and misfiring monitoring system with injection andignition timing;

FIG. 28 shows details in cross-section of a compressor that is suitablefor use, for example, with the engine of FIG. 1;

FIG. 29 is an elevational view of an impeller suitable for use in thecompressor of FIG. 28;

FIG. 30 is a section along line A-A′ of FIG. 29;

FIG. 31 shows a housing being part of the compressor of FIG. 28,

FIGS. 32 and 32a show elevational and sectional views of a diffuser ringof the compressor of FIG. 28;

FIG. 33 is a diagram of a system for measuring and controllingtemperatures of components of an engine embodying the invention;

FIGS. 34 to 44 show, in longitudinal and transverse cross-section,various alternative configurations of engines embodying the invention;

FIGS. 45 to 57 are diagrams of various alternative externalconfigurations of engines embodying the invention;

FIGS. 58a to 58 f are diagrammatical cross-sectional views of part of anengine embodying the invention;

FIGS. 59 and 60 show detail design features of expansion chambers in anengine embodying the invention;

FIG. 61 shows diagramatically a compressor having inlet and outletcontrol valves;

FIG. 62 shows diagrammatically a compressor including multiple(optionally modular) units with outlet control valves;

FIG. 63 is a table that illustrates an expansion pressure profile;

FIG. 64 is a design performance table;

FIGS. 65 and 66 are PV diagram graphs that represent the thermodynamiccycle for the Otto similar and Diesel similar cycles, respectively;

FIGS. 67 and 68 are pressure graphs associated with FIG. 63 for therotor and stator components, respectively; and,

FIG. 69 is a graph that illustrates Ratio of Length to Adiabatic Areavs. Length for a Retort Shaped Chamber.

GENERAL CONFIGURATION

With reference first to FIG. 1, an engine embodying the invention has agas flow path that proceeds generally from right to left in FIG. 1.Combustion air enters the engine at an inlet duct 100, and enters acompressor 110. From there, it proceeds to an intercooler 112, fromwhich it passes through a duct 114 into a combustion assembly 116.Exhaust gasses then leave the combustion assembly 116 (otherwisereferred to as “the hot portion”) and proceed to an exhaust gas turbine118 from where they are vented to atmosphere. A flow of cooling air alsopasses through the intercooler 112, the combustion assembly 116 and theninto the turbine 118. Each of these engine components is constructedaround a shaft 122, which is carried on bearings for rotation about anengine axis A. A fan 120 is carried on the shaft, in this embodimentbetween the intercooler 112 and the combustion assembly 116, to drivecooling air through the engine. For convenience, the inlet duct 100 willbe said to lie towards the “inlet end” of the engine and the turbine 118will be said to lie towards the “outlet end” of the engine.

The construction and function of each of these engine components will bedescribed in further detail below.

Air Induction and Compression

Combustion air is compressed externally of the combustion chamber. Thisis unlike a typical piston internal combustion engine where compressionis carried out in a combustion chamber by a piston; in this embodiment,a multi-stage centrifugal compressor 110 carries out compression.

The compressor comprises first and second rotors 124, 126 each carriedon the shaft 122 fixed for rotation therewith. A rotor is shown in FIGS.2a and 2 b. Each rotor has a generally annular backplate 128 carried ona boss 132 that is secured to the shaft 122 such that the backplateextends normally to the engine axis A.

A plurality of vanes 130,130′ projects from the backplate 128, generallytowards the inlet end of the engine. In this embodiment, there arethirty-two vanes in total, the vanes being alternately long 130 andshort 130′. FIG. 2b shows the arrangement of several vanes, thisarrangement being repeated in equal spacing around the rotor. The longvanes 130 extend from near the boss to the periphery of the backplate128 while the shorter vanes 130′ extend from approximatelythree-quarters of the radius of the backplate outwardly to the peripheryof the backplate. Each vane 130,130′ is curved, such that the outerextremity of the vane 130,130′ lags behind the inner extremity of thevane when shaft is turning in the direction of normal engine operation.

The precise curve and number of vanes is optimised in each rotor 124,126being selected to optimise its efficiency at the intended typical speedof operation for any particular engine. The methodologies by which suchoptimisation can be achieved are well known to those skilled incompressor design.

Each stage of the compressor 110 further comprises a housing withinwhich the rotors 124,126 are contained. At the inlet end, the housinghas an annular outer wall 134 that has a central aperture surroundingthe shaft 122, the aperture being approximately the diameter of theinner ends of the vanes of the first rotor 124. This apertureconstitutes the inlet duct 100. The outer wall 134 lies parallel to thebackplate 128 of the first rotor 124, and is spaced from the vanes130,130′.

The housing further comprises an annular dividing wall 136 that extendsbetween the two rotors 124,126. A central aperture in the dividing wallsurrounds the shaft 122.

An inner wall 138 of the housing is disposed at the outlet end of thehousing. The inner wall closely surrounds the shaft 122 and afluid-tight seal is disposed between the inner wall 138 and the shaft122.

The outer wall 134 and the dividing wall 136 are interconnected aroundtheir peripheries by a curved wall section 140, the inner surface ofwhich is concave. This is known as the “volute”. The dividing wall 136and the inner wall 138 are likewise interconnected.

As the shaft 122 spins, the rotors 124,126 spin with it. The vanes ofthe first rotor 124 drive air radially outwards, drawing air in throughthe inlet 100 duct. Air driven out from the first rotor impinges uponthe curved wall section and is then driven radially inwards between thebackplate of the first rotor and the dividing wall 136. From there, theair is drawn through the aperture in the intermediate wall, from whereit is once again driven radially outwards by the second rotor 126.

As such, the compressor 100 is, in this embodiment, as a two-stageradial compressor, in this embodiment, with an output pressure ofapproximately 9.2 Bar.

Additional design considerations can be applied to the compressor in theconstruction of other embodiments. As is well understood, the flow ofair that the compressor 110 should produce is dependent upon the rate atwhich fuel is consumed in the combustion assembly. In order to meet thisrequirement, the compressor housing can be constructed from a pluralityof similar modules, each module containing a respective rotor. Thus,additional modules can be provided as required to produce a sufficientthroughput of air for the combustion of fuel in the combustion assembly116.

While an engine is operating at a partial or low power output, theamount of air that must be provided in order to support full combustionis less than is the case when the engine is operating at full power.This can lead to inefficiency at partial power, in that the compressor100 is consuming more power than is actually needed to providesufficient combustion air. Therefore, one modification is that may bemade to the compressor is to restrict the amount of air that can enteror leave the compressor (so reducing aerodynamic drag) underpartial-power conditions.

For example, there is shown diagrammatically in FIG. 1 a one possibleconfiguration of the volute of a compressor. The volute has several, inthis case four, similar partitions that each increase in radius from theaxis A in the direction of rotation of the rotor 124, the partitionsbeing interconnected by a radial wall portion 170. At each of the radialwall portions there is an outlet duct 174 for air that has beencompressed within the compressor housing. In this example, one duct 174is always open to provide a supply of compressed air, while the otheroutlet ducts 174 each has an associated valve 176 that can be operatedto selectively permit or prevent flow in the corresponding duct 174. Thevalves 176 may be operable individually or several may be interconnectedfor operation together.

With reference to FIGS. 3a, 3 b and 4, an implementation of a schemewhereby an air access path to some of the vanes of a compressor rotorcan be obscured to resist ingress of air. In this alternativeembodiment, the housing 1140 carries an annular ring 1112 lying in aplane normal to the engine axis A, surrounding the inlet duct 1144, andhaving a diameter such that it lies close to the inner ends of the vanes1130. A plurality of closure flaps 1110 is carried on the ring 1112.Each flap 1110 is formed as a thin plate, curved so as to follow an arccentred upon the engine axis A. Close to one of its ends (the later edgeof the flap encountered in normal rotational motion of the engine) theflap 1110 is secured to the ring 1112 such that it can pivot about anaxis that lies parallel to the engine axis A and adjacent to thecircular locus on which lie the ends of the long vanes 1130. At oneextreme of its pivotal movement, the flap 1110 extends from the saidlocus to an end region of an flap 1110, so substantially closing the airpassage between adjacent flaps 1110 to the vanes 1130. At the otherextreme of its pivotal movement, the flap 1110 projects inwardly fromthe locus, so opening the air passage. In a preferred arrangement, theflaps extend contiguously for approximately three-quarters of theperiphery of the ring 1112.

Movement of the flaps 1110 is controlled by a mechanism shown mostclearly in FIG. 4. Each flap has a spigot that extends through the ring1112, and a crank lever 1114 is carried on the spigot adjacent to theopposite side of the ring 1112. A solenoid actuator 1116 is connected tothe crank lever 1114 through a linking rod 1120. Electrical power can beapplied to the solenoid actuator 1116 to drive the linking rod 1120linearly, this linear movement, in turn, effecting pivotal movement ofthe associated flap 1110 between its extremes of movement. A spring isprovided to drive the linking rod 1120 to the position in which the flap1110 is fully open, this being a fail safe condition, in which theengine will continue to run, in the event of loss of power to theactuators 1116.

The various actuators 1116 are controlled by a control unit to open andclose in response to variations in the demand of the combustion assembly116 for combustion air. One method of controlling the intake ofcombustion air will be described in detail below.

This arrangement may be more suited for application to control air flowto the first rotor 124 where more space is available at the inlet duct100 than there is at the aperture in the dividing wall.

Cooling Air Flow

The fan 120 is mounted for rotation with the shaft 122. The fan 120 actsto cause a stream of air to flow axially through the engine to coolvarious parts of the engine. In particular, the cooling air flowsthrough the intercooler 112 and through the combustion assembly 116.

Upon its exit from the combustion assembly 116, the cooling air flowpasses through a louvre assembly 150. The louvre assembly 150 comprisesa plurality of louvre-like passages each of which tapers in a V-shapedcross-section in the direction of cooling air flow. This subjects flowof cooling air in the desired direction to an impedance less than in thereverse direction. This arrangement reduces the risk of the cooling airbackflushing under pressure from the combustion exhaust gas.

Cooling Combustion Charge

As is well known, forced induction in an engine can give rise to anexcessive charge temperature, with undesirable results such as areduction in volumetric efficiency and a tendency to cause detonation inspark-ignition engines. For this reason, an intercooler 112 is providedto cool the combustion air.

In this embodiment, the intercooler 112 is a toroidal unit through whichthe combustion air can flow. The intercooler is formed as a metalcasting. Internally, the intercooler 112 has a plurality of fins 512over which the combustion air passes, the fins 512 acting to extractheat from the combustion air. Additionally, there are fins 510 formed onthe outside of the intercooler 112, over which the cooling air flows.These external fins 510 act to remove heat from the metal of theintercooler.

Construction of the Combustion Assembly

Within the combustion assembly 116, fuel is burned with the aim ofcausing a torque to be applied to the shaft 122 so that the rotatingshaft can do useful work. In this embodiment, torque is generated at arotor assembly 210 that is rotationally fixed to the shaft 122. Theprocess by which torque is generated includes combustion of fuel incombustion chambers defined between the rotor 210 and a plurality ofstator assemblies 310 in a general arrangement as shown in FIG. 7. Thesecomponents will be described in detail below.

Turning now to FIGS. 7 to 9, the rotor assembly 210 has a peripheralshape of a short cylinder, in that it has a cylindrical outer surface212 centred about the engine axis A, and spaced, parallel faces, normalto the axis A, each circular in shape. The rotor is carried on the shaft122, fixed, in this example by splines, for rotary motion with the shaftabout the engine axis A. As shown in FIG. 7, such motion (when theengine is in operation) is clockwise. The rotor 210 assembly isrotationally symmetric about the axis A. In this embodiment, the rotor210 has a symmetry number of two, such that it appears substantiallyunchanged upon rotation about the axis by 180°.

The rotor 210 assembly includes a one-piece metal rotor casting 220(shown in FIG. 8). The rotor casing is clamped between two generallydisc-shaped end plates 222, as shown in FIG. 9, to form the completerotor assembly. (It should be noted that FIG. 9 illustrates just onehalf of an end plate 222, to the left of the line C—C, the end platebeing rotationally symmetrical about the axis A.) In this embodiment,the rotor casting and the end plates are formed from stainless steel.The use of stainless steel can provide a material of high tensilestrength that is resistant to corrosion, and in particular, to corrosiveaction of sulphur and its compounds. Such corrosion resistance can beimportant in many applications.

Within the rotor casting 220 there is formed a multiplicity of voids.Each of the voids extends axially through the rotor casting 220. Some ofthe voids extend within the rotor to open through a respective aperture216 in the cylindrical outer surface of the rotor 210. Each aperture 216extends to a parallel to the axis so as to approach but stop short ofthe parallel faces 214, therefore leaving a band 260 of metal thatsurrounds the periphery of the rotor casting adjacent to its two axialends. Circumferentially, each aperture 216 extends by the same extent asthe void within. The end plate 222 closes the axial ends of some of thevoids such that their only external opening is through the cylindricalouter surface 212 of the rotor casting 220. Adjacent to axial ends ofothers of the voids, the end plate is cut away to leave open the axialends of the voids. The configuration and the function of the variousvoids will be described in detail below.

The presence of the periphery bands helps to conduct heat away from thehottest parts of the rotor casting, and also helps to strengthen anddamp rotor chamber walls against mechanical vibration. A suitabledeadening substance, such as a high-melting-point wax may be provided tofurther reduce vibration, for example during fine machining of the rotorperiphery.

The voids are of a wide variety of different shapes and sized determinedby the function that they are intended to perform. In each rotationallysymmetric half of the rotor, a plurality of expansion chambers 232, aprimary chamber 234 all of which have an opening at the cylindricalouter surface 212 only. Additionally, there are cooling fluid ducts 236,which are open to both their axial ends, but which have no opening tothe cylindrical outer surface 212. Adjacent to each of the cooling fluidduct 236, the end plate 222 has a cooling fluid aperture 238. (Note thatin this embodiment, one such cooling fluid aperture 238 may surroundseveral cooling fluid ducts 236.) There is also an exhaust chamber 240,adjacent to which the end plate 222 has an exhaust aperture 242.

There is also an inlet transfer chamber 230 is formed as a pair ofcircumferentially extending elongate troughs, each being formed at theintersection of the cylindrical outer surface 212 of rotor casting 220and the axially opposite parallel faces. Adjacent to each of thetroughs, the end plate 222 has an inlet recess 244 that extendssubstantially the length of the trough, but which extends axially onlypart-way through the end plate 222.

Each of the primary chamber 234, each expansion chamber 232 and theexhaust chamber 240 have a shape that will be referred to as “retortshaped”. That is to say, it has a relatively narrow opening at the outersurface 212 of the rotor casting 220, extending through a thin necksection into a bulbous interior. The neck sections are curved such thatthey extend generally in the direction of rotation of the rotor casting220 at an acute angle from a tangent of the outer surface 212. Thepurpose of this shape is to limit heat loss by value of its bulbouscross section. Also to accelerate the exiting gases through the mouth,to improve the impulse effect of the gases in their dance of harmonicfluctuations, that is described later. The shape also assists to createsmooth gas flow and gas rotation.

As the rotor rotates, the first chamber encountered is the transferchamber 230. After an interval (referred to as “the timing gap”) thenext chamber encountered is the primary chamber 234 (also referred to asa “maid chamber”. Then follows the expansion chambers 232 (in thisembodiment, twelve of them). Each successive expansion chamber 232 isgreater in volume than its predecessor. The primary chamber 234 has avolume larger than the first few of the expansion chambers 232. Thetiming gap is equivalent to advance before top dead centre in aconventional Otto cycle engine.

In a spark ignition engine the combustion chamber 316 may be larger thanthe primary chamber to provide enhanced gas fluctuations. The primarychamber may have a volume of between 15% and 35% (for example, 30%) ofthe volume of the combustion chamber. In the Diesel-like cycle thischamber is not so enlarged as it would remove gas prematurely in thefuel injected burn process.

As can be seen in FIGS. 1 and 7, the stator includes two substantiallyidentical stator assemblies 310 carried on a cap control system mountedon engine chassis (not shown). The stator assemblies are disposedrotationally symmetrically around the engine axis A such that one statorassembly is in a position rotated 180° around the axis with respect tothe other stator assembly. Details of the mounting for the stator on thechassis and of the gap control system will be described in more detailbelow.

Each stator assembly includes a stator casting 320, which is clampedbetween two end plates 322. As illustrated in cross-section in FIG. 7and in perspective in FIG. 10, the stator casting 320 is formed as aone-piece metal casting. In this embodiment, the metal chosen isspherical graphite iron. This metal has, to some extent, the property ofbeing self-lubricating.

The stator assembly 310, when in position in an engine embodying theinvention, extends generally in a curve surrounding the engine axis A.An inner surface 312 of the stator casting 320 lies on a locus that is asegment of a circle that is centred upon the rotor axis. The statorcasting 320 also has opposed parallel side surfaces disposed normally ofthe rotor axis against which the end plates 322 lie. A plurality ofvoids is formed in the stator casting 320, each void extending throughthe casting from one of its side surfaces to the other, the ends of thevoids being sealed by the end plates 322. The voids extend to openingsthrough the inner surface 312, and are retort shaped, as describedabove. In the stator, the neck sections of the voids are curved suchthat they extend generally in a direction opposite to the direction ofrotation of the rotor 210 at an acute angle from a tangent of the innersurface. The stator casting 320 is further provided with a multiplicityof fins 334 that serve to dissipate heat from the casting.

In the direction of rotation of the rotor 210, the first chamber in thestator 310 is referred to as the coolant injection chamber 314. Thisretort-shaped chamber is not directly connected with the combustionprocess. Instead, cold air optionally loaded with an oil mist and/orwater droplets, is injected into the coolant injection chamber 314, suchthat the air and oil impinge upon the rotor casting 320. This preparesthe rotor for the imminent combustion sequence.

Subsequent (in the direction of rotation of the rotor) to the coolantinjection chamber is the combustion chamber 316. In this example, thecombustion chamber 316 is retort shaped. A tapped hole 318 is formedthrough the stator casting into the combustion chamber. A spark plug(not shown) can be inserted into the tapped hole 318 such that itselectrodes extend into the combustion chamber 316.

Next to the combustion chamber 316, an inlet passage 324 is formed inthe stator casting 320. The inlet passage 324 is a cylindrical void thatextends axially through the stator casting 320. Ends of the inletpassage communicate with transfer recesses 326 in each of the end plates322. Combustion mixture can enter the transfer recesses 326 throughpassages in either one or both end plates 322. In the formerarrangement, the inlet passage conducts the combustion fixture from thesaid one end plate 322 to the transfer recess 326 in the other endplate.

After the combustion chamber 316 there is a multiplicity (twelve in thisembodiment) of retort-shaped expansion chambers 332. The volume of theexpansion chambers 332 increases sequentially in the direction ofrotation of the rotor 210.

Operation of the Combustion Assembly

With reference now to FIGS. 12a to 12 e and FIG. 13, there is shown acombustion sequence in the engine of FIG. 1. (It must be remembered thatthis sequence of events is taking place simultaneously in both of thestator assemblies on diametrically opposite sides of the rotor.)

First, it should be borne in mind that the inlet passage 324 is filledwith combustion air and fuel mixture under high pressure. This chamberis substantially sealed because the transfer recesses 326 of the endplates 322 abut against the end plates 222 of the rotor assembly 210.

Now, the rotor assembly 210 rotates until the inlet recesses 244 comeinto position radially inwardly of the transfer recesses 326 (FIG. 12a).Combustion mixture can then pass through the inlet recess 244 into thecombustion chamber 316, as shown in FIG. 13.

Following continued rotation of the rotor assembly 210, the passagebetween the inlet passage 324 and the combustion chamber 316, so sealingthe combustion mixture within the combustion chamber 316. The spark plugcan then be energised to initiate combustion within the combustionchamber 316 (FIG. 12b).

Next, the primary chamber 234 comes into alignment with the combustionchamber 316 causing gas to expand rapidly from the combustion chamber316 into the primary chamber 234. As the gas impinges upon the walls ofthe primary chamber 234, it is decelerated, with the result that some ofits momentum is transferred to the rotor. During this transfer, a forceis applied to the rotor that results in a force couple around the engineaxis A, and therefore, a torque is transferred to the shaft 122.Expansion of gas from the combustion chamber is repeated as subsequentexpansion chambers 232 pass the combustion chamber 316, the pressure inthe combustion chamber being successively reduced.

Simultaneously, the primary chamber 234 passes the first statorexpansion chamber 332, and an amount of gas expands from the primarychamber 234 into it. This causes a further small impulse to be appliedto the rotor. This process is repeated for subsequent expansion chamberswith successive reductions in the pressure in the primary chamber 234.

Gasses are taken to exhaust in two ways. Gasses in the rotor can escapefreely once the chambers move beyond the stator, and gas can escape fromthe stator chambers into the rotor exhaust chamber 240.

In an alternative mode of operation, a comparatively large quantity ofwater is injected into the coolant injection chamber 314. This water isconverted to steam in the rotor chambers 232,234, so transforming therotor assembly 210 into a steam raiser. This steam expands from therotor chambers 232,234 into the stator chambers 332 together with thecombustion gasses without dowsing combustion, and so contributes toapplying a force couple to the rotor 210. In this mode, the engineeffectively operates as an internal steam turbine, this being a distinctclass of engine.

It will be noted that if there are (for example) ten chambers in therotor, other than the transfer chamber, ten impulses will be imparted tothe rotor by the gas transference mechanism. If the number of statorchambers is the same as the rotor, although the number of chambers isdoubled, the number of separate impetuses has squared. A total oftenrotor and ten stator chamber will provide one hundred separate impetusesto the rotor, with the gas fluctuating backwards and forwards betweenthe various chambers. These can be considered to be harmonic gasfluctuations of a cadence recursive process. This combined with thedirect force couple acting on the rotor assembly, rather than through asystem of mechanical linkages, together with the rotational speed, iswhat helps to give the engine its power and efficiency.

A key to the engine's performance is that there are not only chambers inthe rotor, but also similar chambers in the stator. Each expansionchamber adds an additional impetus to the rotor, so that in the exampleshown there will be 169 (that is, 132) separate impetuses given to therotor. The expansion process can be termed harmonic gas fluctuations ina cadence recursive process. This combined with the direct force coupleacting on the rotor assembly, rather than through a system of mechanicallinkages, together with the rotational speed, is what helps to give theengine its power and efficiency.

Fuel Injection/Carburetion

Fuel injection or carburetion can be made at any of several places.Examples include: at the input 100 to the compressor 110; within thecompressor 110; at the output of the compressor in the transfer pipingor chamber 114; directly into the combustion chamber 316; or, asdescribed above, via a transfer chamber. Injection or carburetion may,indeed, be made at one or more of these points. Numerous configurationsof compressor(s) and combustion assemblies are possible, but theinjection or carburetion possibilities across these configurationsfollow the basic options described.

Exhaust

Exhaust gasses from the combustion assembly 116 are extracted through atapering annular Venturi 144. At an outlet of the Venturi 144, theexhaust gas combines with the cooling air stream, and the combined gasstreams are drawn into the exhaust gas turbine 118. Under conditions ofhigh power operating, the exhaust gas stream may be of sufficient volumeand speed to drive the turbine 118 and make a net contribution to theoutput power of the engine. The turbine 118 also serves to scavengeexhaust gasses from the combustion 116 assembly, and assists inmaintaining the cooling air stream.

At the exit of the Venturi, there is provided at 152 a plurality ofpassages that taper in the direction of exhaust gas flow, each of whichtapers in a V-shaped cross-section in the direction of exhaust gas flow.This subjects flow of exhaust in the desired direction to an impedanceless than in the reverse direction. This arrangement reduces the risk ofthe exhaust backflushing into the combustion assembly under pressurefrom the cooling air.

The exhaust frequencies from the engine are typically higher than is thecase with conventional engines. For a horizontally opposed two‘cylinder’ equivalent engine of maximum speed N revolutions per secondand n chambers in each of the rotor and stator, the base frequency is 2NHz, with the main harmonic component 2nN Hz. The sound pressure wave maybe reduced by placing a series of Helmholz resonators in the exhaustpipe, as shown in FIG. 14a. At their simplest, the Helmholz resonatorsmay be side chambers 1310 (for example, approximately spherical inshape) into which exhaust gas can expand from an exhaust pipe 1312.

In an alternative embodiment, one, two or more tuneable resonators ofunequal size may be used, as shown schematically in FIG. 14b. Eachresonator 1410 includes a cylinder 1412 into which exhaust gas canexpand from an exhaust pipe 1414. The cylinders are each closed by arespective piston that can be moved to change the volume (and hence theaudio resonant frequency) of the resonator 1410. The tuneable resonators1410 are designed such that the larger one absorbs the base frequency,the smaller one the principle harmonic. The tuning piston 1416 of eachresonator is moved while the engine is in use, the position of each ofthe resonators being coupled to the engine speed by means of a servomechanism 1420. The volume of both resonators 1410 is decreased as theengine speed increases.

Detection of Misfiring in a Spark-ignition Engine

As shown in FIG. 15 (in one embodiment) small sensing coils 1510 and1512 are wrapped around the ignition leads 1514, 1516 that feed thespark plugs 1518 in an engine, for example, as described above. Thecoils 1510,1512 feed opposite sense inputs to an amplifier 1520 of gaindefined by resistance R. A reference voltage V feeds the other input andsets a trigger threshold. When the plugs 1518 operate normally bothcoils 1510,1512 pick up the same induced current and the output of theamplifier 1520 is nearly at zero volts. When a plug 1518 misfires, theoutput of the amplifier 1520 pulses either positive or negative. Suchpulses may be used to trigger an alarm. If a diode D is incorporated inthe feedback path, the amplifier 1520 will self-latch to provide acontinuing indication that misfiring has occurred.

Lubrication

Lubrication of the rotor-stator surfaces may be achieved (as discussedabove) by injection of oil, fine air-oil mist spray, or solid graphite.Alternatively or additionally a lubricant ‘brush’ 1610 may be provided,as shown in FIG. 16. The lubricant brush 1610 includes a body oflubricant material, such as a graphite bar 1612. A spring 1614 holds thebrush against the surface of the rotor 210. The brush is carried on thestator just prior to the combustion chamber 316; the position at whichmaximum efficacy may be obtained.

Rotor/Stator Gap Control

An engine embodying the invention typically operates at speeds far inexcess of conventional piston engines, perhaps up to 30000 rpm. Oneproblem that this presents is that the diameter of the rotor increasesas a result of thermal expansion and centripetal elastic deformation asspeed of the rotor increases. However, simply increasing therotor/stator gap is not a satisfactory solution because this would allowexcessive gas leakage from the various chambers.

Systems may be incorporated into embodiments of the invention to controlprecisely the gap separation between rotor and stator. This process willbe termed dynamic gap control. The objective of either arrangement is tobypass the need for vulnerable sealing tips and rings, although thesemay be employed if desired. Such seals (if provided) are typicallylocated at the rotor or stator chamber cheeks and around the rotorshoulders. In an axial configuration (see below), there is no need fordimension changing, only gap control. However the stator and rotorchambers are much more difficult to manufacture and thrust bearings, orsome form of thrust balancing is necessary. In either design approach,the combination of the rotor's high speed and the fine gap control meansthat ideally no seals are needed, as firstly the gas ‘escape time’ isreduced due to the rotational speed and secondly the gap is sufficientlynarrow to reduce leakage.

A principle objective is to keep the rotor/stator gap constant at allengine speeds. This can be achieved by a control system that: a)measures the gap dimension either directly by contact means or by othersensor technique such as proximity detection or laser beam; b) infersthe gap measurement from component temperatures (rotor and stator)together with rotor speed; or c) is a combination of both types a) andb).

In this embodiment, the gap is controlled by moving the statorassemblies towards or away from the engine axis A, this movement beingcontrolled by a control system. To achieve this, each stator assembly iscarried at its leading and trailing edges on a respective camshaft.Rotation of the camshafts cause consequential movement of the statorassembly towards and away from the engine axis A. The camshafts arearranged for contrarotation so that the forces they apply to the statorassembly 310 are, as near as possible, balanced.

In this embodiment (designated generally as an “expanding jaw”configuration), the radius on the stator inner facing surface 312 isgreater than the radius of the outer surface 212 of the rotor 210 whenit is cold and stationary. This is shown in FIG. 17. These radii aredesigned to be the same when the engine is running at near maximum speedand temperature, as shown in FIG. 18. As the speed of the rotor 310increases and its temperature rises, the stator position is adjustedoutwards by means of a controlled servomotor and mechanical drivingsystem (not shown) to maintain a constant gap distance at the opening ofthe combustion 316. Some compromise of the gap distances occurs at thelast stator expansion chambers 332, in that their gaps will be too wideuntil near full speed and temperature is reached. (In alternativeembodiments, this effect can be reduced by providing more jaws, and/orby segmenting the stator into further segments.) Alternatively oradditionally sealing strips 1710 may be added to the stator cheeks ofthese last chambers 332. The advantage of this dynamic jaw systemdescribed is that the chamber design and manufacture are not complicatedand the rotor can be used for gas transfer without enlarging thetransport areas. Thus the engine design is kept compact and simple, atthe expense of optimum gap dimensions occurring nearer to top enginespeed. It should be noted that the jaw driving mechanism is positioned‘offset’ to ensure that the jaw movement aligns with the two combustionchambers, (line X-Y in FIGS. 17 and 18).

Details of the ‘Tapered’ Embodiments

In alternative embodiments, the rotor/stator gap is controlled byforming the rotor in the shape of a frustum, as shown in FIGS. 19 and20.

In the tapered embodiments, the rotor and stator are both tapered to thesame amount. When the rotor expands due to centripetal forces and boththe rotor and stator expand due to thermal expansion, the rotorsposition is adjusted relative to that of the stator. FIGS. 19 shows theconfiguration of this embodiment before expansion and FIG. 20 shows theconfiguration of this embodiment after expansion. As will be seen,movement of the rotor 1910 axially along the shaft 122 alters thespacing between the rotor 1910 and stator 1912. Movement of the rotor1910 is achieved by its being mounted on a splined portion of the shaft122. An axial end of the rotor assembly 1910 is in contact with a thrustbearing 1914, which is mounted on a collar 1918 that is itself disposedconcentrically with the shaft 122. An outer surface 1916 of the collar1918 is formed with an external screw thread that is in threadedengagement with an internally threaded aperture formed in a supportmember 1926 that is fixed relative to the stator 1912. The collar 1918is constrained for axial movement with the rotor 1910 but can rotaterelative to it. The collar 1918 additionally has a radially projectinggear portion 1920 A servomotor 1922 acts through a gear train 1924, toeffect the rotational movement of the collar, which, through the actionof its threaded outer surface 1916, causes axial movement of the collar1918. This, in turn, alters the gap between the rotor and the stator. Ascompared with the embodiment of FIG. 1, larger dimension transferchambers and port areas may be necessary, unless separate port valvesare employed. However optimum gap control can be provided occurs acrossthe speed range.

Details of the “Axial” Embodiments

With reference to FIG. 21, in another alternative embodiment, combustionand expansion chambers 2110 are defined in facing surfaces of an annularrotor 2112 and stator 2114. Axial movement of the rotor on the shaft 122can be achieved by means of an assembly 2116 similar to that describedin the last-preceding paragraph.

The expanding jaw design however is more of a compromise than thetapered design, but benefits from simpler transfer chamber and primarychamber charging design, in that the rotor can be used for this purpose.This jaw design is described in more detail later on in this patent.

Gap Control Systems

A first gap control system is shown in FIG. 22. In this system, a sensorS detects the gap dimension, and generates an output signal indicativeof that gap. This feeds an amplifier A, which has a set point voltagereference R, for the required gap dimension. The amplifier produces anoutput when there is a difference between the set point and the actualgap that drives a servomotor M, which, in turn, drives a mechanicallinkage L until the gap dimension is restored to the required level.This is a closed loop system. If two detectors are employed across therotor diameter, the output voltages can be fed to a suitable electroniccircuit, such as a microprocessor, to detect eccentricity and wobble.

In the system illustrated in FIG. 23 there is no direct measurement ofthe gap dimension. Instead, a value is obtained from an electroniclookup table T dependent upon the rotor speed, rotor and statortemperatures. The servomotor M is driven to provide the correct gapsetting through the linkage L. This is an open loop system.

In the system shown in FIG. 24 the loop is closed by virtue of thesensor being a strain gauge, which measures the torque on the stator.The rotor-stator design allows non-critical surfaces to interact, suchas at the shoulders of the rotor and stator. This creates drag. Thisenables the additional couple due to a finite amount of rotor slow downto be detected. This is found from extracting the torque output from astrain gauge placed in the rotor's output shaft. When no drag slow downoccurs between the rotor and stator, the output of the two load cellswill be equal. When the gap narrows the drag increases and the output ofthe stator's load cell will increase. This is operated on in a system asdescribed with reference to FIG. 22 by the amplifier and its associatedsystem elements to return the drag to the set point level. Hence the gapis controlled.

Bearing Monitoring

If multiple sensors S1, S2 are employed across a rotor diameter, as inFIG. 25, bearing wobble and eccentricity can be detected. This isperformed by an extra amplifier A1, which detects the difference betweenthe outputs of the two sensors S1, S2. The output from the amplifier A1,is fed to a further amplifier A2, with a set point reference thatprovides an output if deviations are above the set point level. This isused to indicate wear in the bearing beyond acceptable limits.

Combined Bearing and Misfiring Monitoring With Injection and IgnitionTiming

With reference to FIG. 26, there is shown, a non-contact gap controlsystem, suitable for use, for example, with the embodiment of FIG. 1. Aparticular type of sensor is employed which comprises an insulated plate2610 carried on the stator 310 and connected to a high-frequencyoscillator O. The gap is measured by determining the capacitance changebetween the plate and the rotor. Such a change in capacitance can causethe frequency of the oscillator O to change. This is the basis ofproximity detectors suitable for use in embodiments of the invention.The output of the oscillator O is fed to suitable frequency to voltage(F-V) converter F-V, such as a diode pump, whose output voltage feeds asubsequent amplifier stage A, as already described. In operation, whenthe gap closes, the capacitance increases between the plate and theground plane, the oscillator frequency drops and the output from the F-Vconverter decreases, which is acted on by following stages.

This particular type of sensor is useful if it is positioned such that adesigned disturbance on the rotor surface is scanned by it. Such adisturbance might be a transfer chamber, but could also be aspecifically constructed depression or the chamber openings in therotor. The consequence of using this type of sensor is that additionalcircuitry can also detect rotational position of the rotor. This meansthat it can be used to provide dynamic gap control as already described;timing for ignition and injection of fuel with bearing and misfiringmonitoring, all combined in one sensor.

The additional circuitry required in order to achieve this is shown inFIG. 27. The F-V converter operates upon due to the frequency modulatedwave output from the oscillator O to provide a voltage output at circuitpoint a, which includes a sequence of spikes at circuit point b. Thesespikes correspond to the periodic depressions in the rotor. These spikesare integrated by a resistor/capacitor network R₁, C₁ before beingapplied to the gap control amplifier A1 at circuit point c. Theseparation between the spikes is the periodic time t of the rotorrotation. The spikes are further differentiated by a resistor/inductornetwork R₂, L₁ at circuit point d, and rectified by a diode D₁ atcircuit point e. The output at circuit point e is then used to triggerignition and injection control circuits, where used, shown as I and Jrespectively. The approximate voltage waveforms at each of points b, dand e are shown as the upper tracing of each of three insert sections inFIG. 27.

If rotor wobble, for example due to bearing wear, occurs, the frequencymodulation at the oscillator has a further component, which results inan additional voltage ramp term being introduced at point b. The effecton the voltages appearing respective circuit points are at each ofpoints b, d and e are shown as the lower tracing of each of three insertsections in FIG. 27.

The effect on the gap control system is that the gap is widenedmarginally to cater for the wobble. The ramp voltage dV illustrated intracing point b1 is extracted by an additional stage of integration ofsmaller time constant than that used to feed the amplifier A1. This hasa saw tooth output at circuit point f (shown as tracing f1) with muchreduced spikes. The condition of no wobble produces a low output fromthis circuit. The ramp voltage dV can be detected by a referenceamplifier A2 with a latch feedback diode D₂). This will latch high whenthe level of dV) is greater than the reference voltage R). Thisamplifier's output hence provides indication of excess bearing wear. Afurther latch amplifier A3 with a lower reference point may optionallybe provided to detect misfiring vibration in a similar manner.

The gap sensor discussed above can be improved upon by including aninductor in an inductor pit to linearise the response and increase thesensitivity of the sensor. (Using either an inductor or a capacitoralone produces an inverse-square-root law response.)

Compressor Configuration

A multistage compressor 2810 is shown in FIG. 28. Such a compressormight be incorporated into the embodiment of FIG. 1. An impeller 2910suitable for use with the compressor 2810 is as shown in FIGS. 29 and30. The impeller 2910 is designed such that the same impeller castingcan be used for all stages in the compressor. The largest size is thebase for all of the impellers and they are machined to the requiredprofile as indicated by the dotted lines in FIG. 30. Similarly thecompressor 2810 may comprise a housing made up from identical units 3110as shown in FIG. 31 which are machined to the required depth profile,also indicated by the dotted lines and then bolted together to formvarious volute chambers within which the impellers 2910 are contained. Adiffuser baffle 3210 of the compressor 2810 is shown in FIG. 32. Againthis is based on the largest unit, and is machined to fit into theappropriate volute, (see dotted lines in FIG. 32a. The advantage of thismethod of construction is that it is extremely flexible and costeffective. The compressor 2810 is modularly built from only threecastings and can be designed for different stage compression ratios andfor as many stages as is necessary.

If the impeller and volute castings are made of temperature-resistantmaterials, such as stainless steel or nickel steel for the impeller, thecompressor design may also be used for pre or post turbo-chargers or forturbo assistance units. This again extends the application of thedesign.

The design of the rotor and stator of this engine may also be used as aninefficient compressor if the rotor is driven.

Cooling

The rotor and stator temperatures are measured by sensors s1 and s2shown in FIG. 33. Signals from the sensors are fed to a differentialamplifier A1 whose output drives a servo-motor ml which in turn moves afirst slotted disc d1. The first slotted disc d1 lies against a secondslotted disc d2. This diverts the airflow from stator to rotor and viceversa, so that the temperature differential between them is minimised. Afurther amplifier A2 may be provided connected to one of the sensors s1and to a reference voltage R. The second amplifier A2 drives a secondservo-motor m2 which in turn moves a third disc d3 that overlays theother two discs d1,d2. This has the effect of controlling the overallairflow, so controlling the overall temperature of rotor and stator.

Sealing Bars

Where sealing bars are provided in a design, e.g. the expanding jawconfiguration (as discussed below), the bars may be profiled so thatthey are undercut marginally for the section that passes over the rotorchambers. The bars thus rest only against the rotor shoulders, which arenot subjected to as high temperatures as the central chamber section ofthe rotor. The bars can be made of cast iron that has self-lubricatingproperties. End sealing rings may be installed but add to the complexityof the design. The majority of potential gas escape is across thechamber length.

Engine Configurations

Many possible combinations and configurations of the rotor and statorassemblies are possible. Some of these are listed below with thecorresponding outline figure references:

Internal engine configurations:

1. Concentric stator and rotor, or stators and rotors. FIGS. 34a and 34b)

2. Axial stator and rotor, or rotors and stators. FIGS. 35a and 35 b)

3. Mother (combustion) chamber or chambers in the stator or stators.FIGS. 36a and 36 b)

4. Mother chamber or chambers in the rotor or rotors. FIGS. 37a and 37b)

5. Unopposed chambers in the rotor and stator or rotors and stators.FIGS. 38a and 38 b)

6. Opposed chambers in the rotor and stator or rotors and stators. FIGS.39)

7. Expanding jaw sectioned stator or stators for concentric formats.FIG. 39)

8. Tapered stator and rotor or stators and rotors for concentricformats. FIG.

9. Sliding rotor or stator, or rotors and stators for axial formats.FIG. 41)

10. Compensated rotor bob weight for concentric formats FIG. 42)

11. Rotor only or rotor and stator exhausting FIGS. 43a and 43 b)

12. Gas cooled or fluid cooled rotor and stator, or combinations FIGS.44a and 44 b)

External Engine Configurations

There are many external configurations of the engine possible. One ofthe simplest, and several variations, have already been described. Alist of some of the more important external configurations will bedescribed below. A special syntax has been developed to describe theseconfigurations, the grammar of which precedes the list. Inter-stagecooling between compression stages has not been included so as to limitthe number of examples. This can be applied at any juncture between twoor more compressors, or between the stages within a multistagecompressor set. In order to achieve the compression ratio needed,compressors will normally be multistage. Centripetal or axialcompressors are both able to be used:

Grammar:

i) The working fluid flow is left to right. Turbine expansion determinesthe sequence.

ii) Compressors are denoted C, turbines are denoted T and are separatedby commas in a set.

iii) Compressor and turbine sequences are identified by subscripts.

iv) Compressor-turbine sets carry the same subscripts.

v) Cascaded compressors carry the same dot products, as do turbines.

vi) The power output turbine is in bold type.

vii) Isolated turbines are preceded by a plus sign and are bracketedwith dual feed turbines.

viii) An assistance turbine on the same shaft is in italics.

ix) Switching is indicated thus I.

External Configurations:

1. {C,T} Single spool compressor turbine set with output from theturbine. FIG. 45)

2. {C1.C2,T1.T2} Single spool compressor turbine set withpost-compression turbo-charging. FIG. 46)

3. {C2.C1,T1.T2} Single spool compressor turbine set withpre-compression turbo-charging. FIG. 47)

4. {C3.C1.C2,T1.T2.T3} Single spool compressor turbine set with pre andpost compression turbo-charging. FIG. 48)

5. {C1,(T1+T2)} Compressor turbine set with isolated main outputturbine. FIG. 49)

6. {C1.C3,(T1+T2).T3} Compressor turbine set and isolated main outputturbine with post-compression turbo-charging. FIG. 50)

7. {C3.C1,(T1+T2).T3} Compressor turbine set and isolated main outputturbine with pre-compression turbo-charging. FIG. 51)

8. {C4.C1.C3,(T1+T2).T3.T4} Compressor turbine set and isolated mainoutput turbine with pre and post compression turbo-charging. FIG. 52)

9. {C1,T1.T2} Single spool compressor turbine set with post expansionturbine assistance. FIG. 53)

10. {C2,T1.72 C2,(T2+T1)} Single spool compressor turbine set with postexpansion turbine assistance and switching to isolated main outputturbine. FIG. 54)

11. {C1,T1.T3 C1.C2,T1,T2,T3} Compressor turbine set with post expansionturbine assistance supplemented by switched post compression turbocharging. FIG. 55)

12. {C3.C1.C2,T1.T2.T3.T4} Compressor turbine set with post expansionturbine assistance and pre and post turbo-charging. FIG. 56)

External Combustion Engine

In a further embodiment of the invention, combustion of fuel takes placeexternally of the unit. The invention may be applied to externalcombustion units such as steam engines, or pre-heated hot gas engines.As shown in FIG. 57 the engine design is basically the same, except thatno compressor stage is employed. Steam or hot gases are raised in aboiler B (or a producer unit P). Additionally, as the workingtemperatures are lower, the constraints on design are much lessstringent in many respects, particularly in the realm of sealing andthermal expansion compensation. With steam as the working fluid, watermay be recovered by use of a condenser C:

Engine Design Permutations

It can be seen that between the internal configuration (12 basicformats); the gap control regime (3 basic formats) and the externalconfiguration (12 basic formats), there are over four hundred possible,simple permutations of the basic design options.

Diesel Like Version

A diesel like cycle version of the engine differs in that highercompression ratios are employed, and that, as described earlier, thereis no maid chamber, or at most a smaller maid chamber. If this werepresent or too large it would remove part of the working fluid (burninggases), prematurely. The diesel cycle requires injection of fuelthroughout the power stroke equivalent. Hence it is important that nottoo much volume of the gases is removed too early from the combustionchamber during the initial part of the burn process. Fuel injection maybe into the combustion chamber directly, or into a pre-burn chamber asin light power diesels. In all cases however the diesel engine cycleequivalent in this engine is transformed into a high speed, high powerand high efficiency cycle, particularly if the horizontally opposedconfiguration is employed; which can eradicate much of the diesel‘knock’ noticeable with conventional reciprocating diesel engines.

Overall Engine Appearance and Assisted Cooling

An engine design similar to that shown in FIG. 7 is shown in FIGS. 58ato 58 f.

The cross section of this engine across the rotor r and stator sassemblies shows fourteen rotor and fourteen stator chambers. Thisincludes the rotor and stator power exhaust ports, for each of thecylinder equivalents of this horizontally opposed configuration. Each‘cylinder’ hence provides 196 separate power impulses during the powerstroke equivalent. Carbon brush lubrication is provided at cb. Sealingbars are provided on the last chambers of the stator at sb. The statorassembly is made of two halves that conform to the ‘expanding jaws’design discussed above. In FIG. 1 a cross-section through the completeengine is shown, with its four-stage centripetal compressor unit 110.The engine is an air-cooled Otto-like unit. Air passes through the rotorcooling fluid ducts 236 and over the stator cooling fins 334, attachedto the stator assemblies 310. Additional cooling is achieved whenrequired, as at maximum engine output, by injecting a fine water sprayinto the air stream for example, at the air intake 100, or downstreamtherefrom.

A turbine assistance unit 118 is provided on the same shaft, it ispowered from the stator exhaust via the rotor exhaust port. This is fedby means of a venturi 144, which increases the velocity of the exhaustgases hence matching them to the impeller rate. If a fuel burner were tobe included in the configuration, a full gas turbine effect would beproduced. As the turbo assistance impeller is cast from the same mouldsas those of the compressor, the air passage sequence through thecompressor is reversed to that which might be thought more logical.However with the inclusion of pre and post turbo-chargers (nextparagraph) this is of no consequence, since extra piping has beenprovided to feed these units.

Additional pre and post turbo chargers may be fitted to thisconfiguration. The unit is a {C1.T1.T2} turbo-assisted type. If pre andpost turbo charging is added, it is defined as a {C3.C1.C2,T1.T2.T3.T4}configuration with the turbine expansion sequence of ‘main’ to ‘post’ to‘pre’to ‘assisted’.

There are two exhausts in the stator and the possibility of two in therotor, if the rotor is configured to exhaust the stator. In this lattercase the exhausts may operate independently on the turbo-chargers. Newexhaust configurations are possible such as {C3.C1.C2,T1.t2.T2.T3}, or{C3.C1.C2,T1.t2.t3.T2}, where the lower case indicates a rotor exhaust.In the former example, the assistance turbine alone is driven by therotor exhaust, as has been described above. In the latter example thepost and pre-chargers are driven by the rotor exhaust whilst theassistance turbine alone is driven by the stator exhaust. The syntax mayfurther identity between multiple stator exhausts, by furthersubscripts; {C,2.C1.i.C₂ 2,T1.t2.T₁ 2.T₂ 2} is the same as the firstconfiguration, but defines that each stator exhaust separately drives aturbo charger and the common rotor exhaust drives the assistanceturbine. This identifying method may operate over as many exhausts asnecessary.

It should be noted that turbo-assistance provides additional ‘free’exhaust power to drive the multi-stage compressor. Turbo pre-chargingallows additional altitude to be achieved in aero-engine applicationsagain free from the exhaust. Turbo post-charging provides an additionallevel of compression, again free from the exhaust. This is particularlyuseful in that the compressor can be made small and to revolve at ahigher revolution rate than the main engine. These latter two ensure amore even compression performance over the engine speed range.Inter-cooling can also be added to the engine between the variouscompression stages to increase volumetric efficiency. The definition forthe illustrated unit in FIG. 7 then becomes: {C₁ 2.i.C1.i.C₂ 2,T1.t2.T₁2.T₂ 2} for two inter-stage coolers.

Considerations Relating to Design of the Expansion Chambers Chambershape, ‘cupulets’, ‘cupulet tuning’, ‘aperture tuning,’ ‘packing’ &‘ventricles’:

In FIG. 59 the cross sectional appearance of the rotor expansionchambers is shown. As has been described earlier, these are the shape ofan old-fashioned style retort, with a thinning neck section 5910attached to a bulbous body 5912. The purpose of the neck 5910 is toaccelerate the gas efflux and hence create maximum impulse levels uponthe rotor 210. The shape of the bulbous body 5912 is designed tominimise heat loss by providing the maximum volume possible for a givensurface area.

The energy transfer mechanism is that of ‘gas vectoring’ when gas/fluidis transferring from stator chamber to rotor chamber. It is that ofNewtonian reaction when gas/fluid transfers from rotor to stator.

In FIG. 59 it can be seen that the gases entering a chamber, when it isreceiving fluid, rotate in the bulbous cavity 5912. This means that someof the gas energy remains in the gas rotation. This remaining energy maybe transferred as additional impulse power by including devices 6010known as cupulets to the gas facing edge in the chamber. See FIG. 60.The cupulets 6010 break up the gas flow and thereby extract most of thevelocity energy of the impinging gas. Their design is similar to that ofhalf an arrowhead. Each cupulet includes a cup section that impedesincoming gas that faces on to it, and a ramp section that allows exitinggas to escape without much impediment.

The consequence of extracting this velocity energy is that when thechamber next is a donator chamber, the exit velocity is reduced. This inturn means that the subsequent kinetic energy is reduced as is theimpulse power and the gas is delivered over a longer time period. Thusthe cupulets 6010 may be used particularly in the early stages ofcadence-recursive expansion to slow down and match entering and exitinggas velocities to the ‘exposure’ time that these early chambers aresubjected to. The technique is termed cupulet tuning.

Also by using different aperture widths (in particular, reducing thewidths) for the earlier chambers in the expansion sequence, andsubstantially wider apertures for the latter, larger chambers, theaperture times can be matched to the gas velocities. Hence the gas fillsa chamber or empties it throughout the whole of the ‘exposure’ period.The objective here is to ensure that up to maximum engine speed, fullchamber filling and emptying still occurs.

The general effect between cupulet and aperture tuning is one ofbroadening the engine power band. At lower engine speeds and lower powerlevels, the gas velocities tend to be lower. The aperture tuning effectpredominates as the cupulets play less of a role. At higher enginespeeds and power levels, the gas energies and hence velocities arehigher. Under these conditions the cupulets 6010 are correspondinglymore disruptive to the gas flows, reducing the velocities accordingly.The components of this can be seen in FIG. 7.

As a consequence of the retort shape, and the fact that chambers 232have to be closely spaced, particularly in the rotor, the neck 5910 isnormally to one side of the chamber body. In the rotor 210, the chamberpacking in conjunction with the rotor curvature, results in mid-numberedchambers deviating from the ideal and having ‘S’ shaped formats in crosssection. Additionally the rotor 210 carries air cooling chambers 236 or‘ventricles’ which are positioned under and around the rotor chambers.See FIG. 7).

Chamber Dimensions

As was described earlier, the chamber aperture widths are smaller forthe first chambers. This excludes the mother (combustion) and primarychambers, as they are proportionally larger. For constant velocities ofgas, the aperture width should be proportional to the chamber volume.However, practical design constraints normally mean that this ideal hasto be departed from.

Computer modelling of the expansion process shows that not only shouldthe primary chamber 234 be around 30% of the mother combustion chamber316 in an Otto-like cycle, but also the subsequent stator and rotorchambers should have volumes that increase in an exponential-likemanner. The first expansion chamber 232 after the primary chamber 234should be between 2% to 5% of the combustion chamber 316. Also tomaximise power output the chamber lengths should be prescribed tonormally a fixed ratio of length to volume of any chamber volume.

The length of a chamber, for any given shape of chamber, determines howmuch heat energy is lost by gas while in the chamber. The ratio of thelength to the chamber volume and hence the diameter should remainconstant. This means that the chamber length should increase with thevolume. This is termed ‘chamber length adaptation’. This adds anothercomplication to the rotor/stator designs and hence complicatesmanufacture. It also means that the smaller chambers will take up moreof the rotor/stator perimeter, because the chamber diameters will bebigger than If a constant length, as set by the combustion chamber 316,had been used. The incorporation of length adaptation is thus not sostraightforward. It is not included in the design shown in FIGS. 7, forthe above reasons.

A more detailed FIGS. 58a to 58 f is shown which is a concentrichorizontally opposed format with two sets of stator and rotor chambersand the mother chambers in the stators. The stator is of the expandingjaw configuration. Both the rotor and stator assemblies exhaust. Thistype of design provides two power stroke equivalents per revolution permother chamber, compared to a single cylinder four stroke reciprocatingengine's one power stroke per two revolutions. This means that thisdesign will theoretically have a power output level 4 n, where n is thespeed ratio at maximum revolutions between the rotary design and thereciprocating design.

The expanding jaw configuration provides simplicity in transfer chamberarrangements. In FIGS. 58a to 58 f, the power stroke can be seen inoperation. In 58 a the fuel gas mixture is transferred in to the motherchamber, the equivalent of induction. In FIG. 58b it is ignited. In FIG.58c the first chambers are engaging; the power stroke commences. In FIG.58d, the first rotor chamber is exhausting. This is a power exhaust. InFIG. 58e, the first stator chamber is exhausting. Again this is a powerexhaust. In FIG. 58f both rotor and stator exhausts are coupled and thecycle is ready to be repeated.

Combustion Chamber Choking

If an engine embodying the invention is not required to produce themaximum power theoretically obtainable from the combustion assembly, itsefficiency may be improved by so-called combustion chamber choking. Thisis achieved by inserting a sleeve into the combustion chamber 316 in thestator casting 320. The sleeve is generally C-shaped, having an outersurface of generally the same cross-section as that of the combustionchamber 316. Holes are formed in the sleeve where required to enablespark plug and/or injectors or other apparatus to penetrate into thechamber.

The effect of the sleeve is to reduce the volume of the combustionchamber, but otherwise to leave its construction and function unaltered.This produces a substantially direct trade-off between a loss of maximumpower and a gain in fuel efficiency.

Flow Restriction in the Compressor

As was discussed above, some embodiments permit portions of thecompressor to be selectively closed. One particular benefit of doingthis is to prevent surging of air flow in the compressor.

It is recognised that a centrifugal compressor typically has a pressureoutput that rises to a peak as rotor speed increases, up to a maximumpressure value, whereafter, as rotor speed continues to increase, thepressure falls off. Moreover, at low speed, the compressor can present acyclically varying load on the input shaft, which can cause a cyclicvariation in the speed of the input shaft; a phenomenon known as“surging”. It has been found that the variation in pressure and theoccurrence of surging can be minimised by control if the air flowthrough the various compressor stages. In general, an aim of suchcontrol of air is to ensure that each stage of a multi-stage compressor,or each of several parts of a multi-stage compressor delivers as near aspossible a steady output, and operates as efficiently as possible.

With reference to FIG. 61, there is shown a diagrammatic representationof the embodiment described above incorporating the modifications shownin FIGS. 1a, 3 a, 3 b and 4.The inlet duct 100 is provided with aircontrol flaps 1110 as shown if FIGS. 3a, 3 b and 4. These can beconsidered to act as inlet valves IV1, IV2 for segments of the firstcompressor rotor 124. At low speeds, all of the flaps 1110 are closed,so that air can flow into the rotor 124 through the section of the ring1112 which does not carry flaps. Thus, a small amount of air is handledefficiently by a small segment of the rotor 124. As speed increases,further flaps 1110 are opened (effectively opening further valves) untilthe entire rotor 124 is operational. Similarly, the output from thesecond rotor at low speed is taken from just one part of the volute withthe output valves OV1, OV2 and OV3 being closed. As speed increases,these valves are progressively opened so increasing the extent to whichthe second rotor 126 is used.

An alternative arrangement is shown in FIG. 62. In this arrangement,three similar single-stage or multi-stage compressors C1.1, C1.2, C.3are connected in parallel. The output of two of these compressors iscontrolled by a valve V1, V2 that selectively allows or prevents air toflow from the compressor. At low speeds, and low air volumes, bothvalves V1,V2 are closed, and air flow is handled by just one of thecompressors C1. As air flow increases, the valves V1 and V2 are openedin turn, thereby sharing the air flow between the compressors C1, C2,C3.

Both of these arrangements, amongst other possibilities, can be set upto ensure that the air flow through each compressor, or through eachrotor section, is as near as possible optimal.

Mathematical Design Equations

The cadence recursive expansion obeys a stepped adiabatic differentialprocess. This is defined by the equation:${{Pn} \cdot m} = {{Pn} - {1 \cdot m} - 1 + \frac{\left( {{Pn} - {1 \cdot m} - {Pn} - {1 \cdot m} - 1} \right){Vm}\quad \gamma}{\left( {{Vm} + {Rn} - m + 1} \right)\gamma}}$$\begin{matrix}{{\text{where:}\quad V} = \quad \text{stator volumes}} \\{R = \quad \text{rotor volumes}} \\{\gamma = \quad \text{ratio of specific heats}} \\{m = \quad \text{step count}} \\{{fi} = \quad \text{stator chamber number}}\end{matrix}$

Thermodynamic Cycle:

The thermodynamic cycle is represented in the PV diagrams in FIG. 65(graph 1) for the Otto similar cycle and FIG. 66 (graph 2) for theDiesel similar cycle. The differences in the new cycles is in thehot-end ‘cadence recursive’ expansion process.

Cadence-recursive Expansion Pressure Profile:

In FIG. 63 (Table 1) a typical expansion pressure profile is shown, withthe associated graphs shown in FIGS. 67 and 68 (graphs 3 a and 3 b) forthe rotor and stator components.

The Chamber Optimisation Equation is:

For a ‘retort’ shaped chamber the output power is defined by theformula: $P = \frac{K \cdot L}{A^{({{\gamma/\gamma} - 1})}}$

Where:

K=constant of proportionality

L=length of the chamber

A^((γ/γ−1))=adiabatic surface area of the chamber

This produces a curve as shown in FIG. 69 (graph 4).

The retort nozzle design equation is:$V = \sqrt{2\frac{{PA}_{1}}{\rho \quad A_{2\quad}}}$

Where:

V=gas or fluid velocity

P=differential pressure acting

A1=area at the entrance to nozzle

A2=area at the exit off the nozzle

ρ=density of the gas or fluid

Engine Power Equations:$I = {\cos \quad {\varphi \cdot \frac{V^{2}}{2\quad {dA}}}\sqrt{{PK}\quad \rho}}$

Where:

I=impulse acting on a single chamber=angle of incidence of the actinggas or fluid

V=volume of gas or fluid transferred (volume of chamber)

P=differential pressure at start of transfer of gas/fluid

K=ratio of the nozzle entrance to nozzle exit areas

D=density of the gas or fluid

d=deceleration distance gas or fluid travels

A=area of nozzle entrance

And ${It} = {S \cdot {rps} \cdot {\sum\limits_{1}^{n}I}}$

Where:

It=total impulse per second

S=number of power ‘strokes’ per revolution

rps=revolutions per second

n=number of chamber interactions (usually n1.n2, where n1 is the numberrotor chambers and n2 is the number of stator chambers)

Unequal Compression and Expansion Ratios:

Unlike a normal reciprocating engine, the compression ratio andexpansion ratios of this engine may be different, since compression andexpansion are carried out independently, not in the same cylinder, as isthe case of a reciprocating engine. This means that not only does ahigher compression ratio mean greater efficiency for the engine, so doeshigher expansion. If the compression and expansion ratios are matchedthen the engine is said to be ‘of unit ratio’. If the expansion ratio isgreater than the compression ratio, then the engine is said to be ‘overratio’. If it is less it is ‘under ratio’.

The normal constraints of pre-ignition apply to the compression ratio.There is no theoretical limit to the expansion ratio except that imposedby practical engine size and whether the exhaust gases are to be usedfor the various forms of pre, post or assisted turbo charging. If someturbo-charging is desired, then the engine is made either of unit ratioor marginally over (e.g. 1.2 to 2.0).

WR=ER/CR

Where: WR = working ratio or ‘ratio’ ER = expansion ratio CR =compression ratio

Design Rules for an Efficient Engine:

1. The compression ratio shall be as high as possible. The limit isbefore the onset of pre-ignition in the Otto-like cycle. (Otto-liketypically 9:1 to 12:1; Diesel-like 22:1 to 35:1)

2. The expansion ratio shall be as high as possible commensurate withengine size and exhaust loading of turbo charging I assistance. This isexpressed relative to the compression ratio and is termed the workingratio. (Typical ratio range is 1.2 to 2.0.)

3. Engine running temperatures should be as high as possiblecommensurate with material strengths. (Typically 200° C. to 400° C.)

4. The ignition, or mother chamber and other chambers shall be retortshaped with high nozzle ratios commensurate with matching gas speedswith engine rotation rates. (Typical range is 2.0:1 to 4.0:1.)

5. The ignition (mother) chamber and other chambers shall have a lengthwhich is as large as possible commensurate with loss of heat. (Typicalis 10 cm for a 100 ml volume chamber.)

6. The first rotor chamber (maid) should be larger than the immediatefollowing chambers. (Typically 15% to 35% of the mother chamber volume,for an Otto-like cycle and 5% to 10%, for a Diesel-like cycle.)

7. The total number of chambers shall be as large as possible, tomaximise the ‘n2’ effect, commensurate with engine size and minimisingheat loss. (Typical total count is 20 to 40)

8. Flame lengths for the first chambers of the rotor and stator shouldbe as short as practical. (Typically the maid depth is 40% of the motherdepth for an Otto-like cycle and 20% for a Diesel-like cycle)

9. Chambers in both the rotor and stator, except for the maid chamber,shall increase in volume in an ‘exponential’ fashion. (Starting volumesare typically 2% to 5% of the mother chamber volumes)

10. Chamber ‘aperture widths’ should increase (proportionally) withchamber volumes, (under constant gas velocity conditions).

11. Expansion chambers should have ‘cupulets’ on gas front facingsurfaces, particularly for ‘initial’ chambers and rotor chambers.

12. Engine revolutions shall be as high as possible to match flamespeeds, commensurate with rotor material tensile strength. (Maximum rpmis typically between 20,000 and 50,000)

13. The angle of incidence of the chamber nozzles should be as close tozero as possible. (Typical ranges is 10 to 20 degrees)

14. Gap dimensions between stator and rotor should be as small as iscommensurate with engine lubrication and stability. (Typically 0.005 to0.03 mm)

Performance Table:

A typical design performance table is given in FIG. 64 (Table 2). Thistable relates to the Otto-like engine configuration in FIGS. 1 & 7 inthe main body of this application. The engine output of turbine is of1.2 litre capacity for a single module core. Generally all rules ofdesign stated above have been applied to this engine.

Specific Points of Interest are as Follows:

1. The high speed of rotation of the engine of 30,000 rpm (rule 12).

2. The high maximum specific shaft output of 1.0 megawatts (1340 BHP).Double this for a two-core module of 2.4 litres capacity.

3. The total possible engine output of 1.4 megawatts, when turboassistance is applied. Double this for a two core module of 2.4 litrescapacity.

4. The designed mechanical efficiency improvement of nearly 34% (rule13).

5. The compression ratio (non turbo-charged) of 9.12:1 (rule 1).

6. The expansion ratio of 12:1 giving an ‘over ratio’ of 1.32 (rule 2).

7. The high power to weight ratio of 47.8 KW per Kg (29 BHP per lb).

8. The operating temperature of 200° C. (rule 3).

9. The take up and tick over rates of 2,000 and 5,000 rpm respectively.

10. The number of chambers is including power exhausts is 28 (rule 6).

What is claimed is:
 1. An engine including a combustion assemblycomprising a rotor and a stator, in which a combustion chamber isdefined in the stator and a fluid receiving chamber is defined in therotor, in which combustion gas can expand from the combustion chamberinto the receiving chamber, whereby momentum is transferred from thecombustion gas to the rotor, in which the rotor has a plurality of rotorexpansion chambers of successively increasing volumes into whichcombustion gas can expand in turn, and the stator has a plurality ofstator expansion chambers of successively increasing volumes into whichgas can expand from the chambers of the rotor.
 2. An engine according toclaim 1 in which the receiving chamber is of a volume larger thanseveral of the rotor expansion chambers.
 3. An engine according to claim1, in which the rotor has a transfer chamber through which combustiongas can pass into the combustion chamber during a portion of therotation of the rotor.
 4. An engine according to claim 1, in which thereis provided spark ignition apparatus in association with the combustionchamber for igniting a charge of combustible fluid received therein. 5.An engine according to claim 4 in which the ignition apparatus includesa spark plug.
 6. An engine according to claim 1, in which either one orboth of the rotor and stator is formed from a material that hasself-lubricating properties.
 7. An engine according to claim 6 in whicheither the rotor or the stator are formed from spheroidal graphite iron.8. An engine according to claim 1, having an oil mist injector operativeto inject an oil mist into a space between the rotor and the stator. 9.An engine according to claim 8 in which the oil mist is injected at aposition in advance of the combustion chamber.
 10. An engine accordingto claim 1, having a lubricating brush to add lubricating materialbetween the stator and the rotor.
 11. An engine according to claim 10 inwhich the lubricating material is graphite.
 12. An engine according toclaim 1, in which the rotor is shaped as a disc having chambers openingto the periphery of the disc.
 13. An engine according to claim 1, inwhich the rotor comprises a rotor assembly that includes a rotorcasting.
 14. An engine according to claim 12 in which the rotor castingis shaped as a disc, having peripheral openings into voids formedtherein.
 15. An engine according to claim 14 in which the rotor assemblyfurther comprises end plates secured to the rotor casting to close thesevoids axially.
 16. An engine according to claim 13 including severalrotor castings assembled together between endplates to provide acombustion assembly of greater combustion capacity.
 17. An engineaccording to claim 16 in which a spacer is disposed between adjacentrotor castings to aid in removal of heat from the combustion assembly,and from the rotor castings in particular.
 18. An engine according toclaim 17 in which the spacer includes a through passage in alignmentwith cooling fluid ducts of the rotor castings.
 19. An engine accordingto claim 1, in which the stator comprises a stator assembly thatincludes a stator casting.
 20. An engine according to claim 19 in whichthe stator casting is shaped as to partially surround the rotorassembly, having openings into voids formed therein.
 21. An engineaccording to claim 20 in which the stator assembly further comprises endplates secured to the stator casting to close these voids axially. 22.An engine according to claim 21 in which several stator castings may beassembled together between endplates to provide a combustion assembly ofgreater combustion capacity.
 23. An engine according to claim 22 inwhich a spacer is disposed between adjacent stator castings to aid inremoval of heat from the combustion assembly, and from the statorcastings in particular.
 24. An engine according to claim 23 in which thespacer is formed with holes to link the combustion chambers of thevarious stator castings in an axial direction.
 25. An engine accordingto claim 1, having a gap control system for controlling a separationbetween the rotor and the stator during operation of the engine.
 26. Anengine according to claim 25 in which the-gap control system operates tomove the stator radially with respect to the rotor.
 27. An engineaccording to claim 1, in which the rotor is shaped as a frustum, havingchambers opening to its periphery.
 28. An engine according to claim 27in which the stator partially surrounds the rotor.
 29. An engineaccording to claim 27 having a gap control system for controlling aseparation between the rotor and the stator during operation of theengine.
 30. An engine according to claim 29 in which the gap controlsystem operates to move the stator axially with respect to the rotor.31. An engine according to claim 25, in which the gap control systemincludes a non-contact sensor.
 32. An engine according to claim 31 inwhich the sensor operates by capacitive sensing, inductive sensing or acombination of capacitive and inductive sensing.
 33. An engine accordingto claim 1, in which the rotor and stator are both disc shaped, thecombustion chamber being defined between flat faces of the rotor and thestator.
 34. An engine according to claim 1, further including acompressor for supplying combustion air to the combustion assembly. 35.An engine according to claim 34 in which the compressor is driven by therotor.
 36. An engine according to claim 35 in which the compressor andthe rotor are carried on a common shaft or upon interconnected coaxialshafts.
 37. An engine according to claim 34 in which, in a sparkignition configuration, the compressor delivers combustion air at apressure in the range of 4 to 7 Bar, and in a compression ignitionconfiguration, the compressor delivers combustion air at a pressure inthe range of 9 to 15 Bar.
 38. An engine according to claim 34 in whichan intercooler is disposed between the compressor and the combustionassembly operative to remove heat from the combustion air.
 39. An engineaccording to claim 33 in which, in a spark ignition configuration, thecompressor delivers combustion air at a pressure in the range of 6 to 12Bar, and in a compression ignition configuration, the compressordelivers combustion air at a pressure in the range of 20 to 30 Bar. 40.An engine according to claim 1, in which fuel is injected into a streamof combustion air externally of the combustion assembly.
 41. An engineaccording to claim 1, in which fuel is injected into a chamber withinthe combustion assembly.
 42. An engine according to claim 1, in whichwater is introduced into the combustion chamber together with air andfuel.
 43. An engine according to claim 42 in which, during combustion,the water vaporises and expands into the receiving chamber and transfersat least some of its momentum to the rotor.
 44. An engine according toclaim 1, in which the stator and/or the rotor includes a casting betweenend plates.